1. Field of the Invention
This invention relates to a surgical electrode and, more particularly, to a temporary cardiac pacing wire having a bioabsorbable anchor for anchoring the wire in a heart.
2. Description of the Related Art
Devices to stimulate or regulate cardiac function have been known and used for decades. They involve a power source (pacemaker) and a surgical electrode to attach the source to the heart. They are generally of two types.
Implantable pacers are intended for long-term use and, as the name suggests, are entirely implanted in the body. The other type is intended for temporary use. The pacemaker is located outside the body and is connected to the heart by a surgical electrode called a "temporary pacing wire." Although surgical electrodes are used for preparing electrocardiograms and other applications, for the sake of brevity, the description that follows is focused on temporary pacing wires. In general, such connectors are constructed of a number of fine, stainless steel wires twisted together to form a single, flexible, multi-strand electrode wire. The major portion of the wire is insulated with a polyethylene, polytetrafluoroethylene, silicone, nylon, or other nonconducting coating, with a short length of wire at either end left uninsulated. To the distal uninsulated end of the electrode wire there is attached, by swaging or other means, a fine curved needle for piercing the heart tissue to place the uninsulated end of the electrode in the myocardium. At the proximal end of the electrode wire is affixed a straight (e.g., Keith-type) cutting needle for piercing the thoracic wall to lead the electrode to an outer point for connection with the pacemaker. Once that has been accomplished, the needle, or the sharp, pointed end of it, is clipped off and the electrode is ready to be attached to the pacemaker as required to stimulate or regulate the beating of the heart. A single setup involves two electrodes; i.e., two temporary pacing wires.
During the time that the temporary pacing wire is performing its function, a distal end of the electrode wire must be anchored in the heart. The anchor must be secure, lest the continually beating heart cause the wire to be expelled from the heart. When the need for the pacing wire has passed, it is necessary to remove from the body the wire that runs from the external pacemaker to the electrode in the heart. Thus, the requirements for a temporary pacing wire are to some extent in conflict. It must securely attach the electrode wire to the heart during an initial period, then be easily removed from the heart without reopening the surgical site.
U.S. Pat. No. 3,902,501, issued on Sep. 2, 1975 to Citron et al., discloses an endocardial electrode that has a plurality of tines that extend from the electrode adjacent to the tip and form an acute angle with the electrode body. The tines are preferably restrained during insertion of the device.
U.S. Pat. No. 4,444,207, issued on Apr. 24, 1984 to Robicsek, discloses a method of anchoring a temporary pacing wire that has a wire conductor with a curved needle at its distal end. The method involves passing the curved needle through the wall of the heart and then through a disk-shaped button. The button is moved into contact with the heart and, after the distal end of the wire is severed, the button serves to retain the wire in a fixed position relative to the heart wall.
U.S. Pat. No. 4,628,444, issued on Dec. 16, 1986 to MacGregor et al., discloses a permanent cardiac pacing lead that has an electrode with a plurality of biodegradable fins adjacent to its tip. The electrode becomes permanently fixed in the heart over a period of weeks, during which time the fins are gradually absorbed.
U.S. Pat. No. 5,314,463, issued on May 24, 1994 to Camps et al., discloses a bipolar temporary pacing wire whose distal end has a fixation coil that is embedded in the heart wall for retaining the device in the heart.
None of the prior art pacing wire devices combine a bioabsorbable anchor with the means to remove the other elements of the device with minimal heart trauma.